Co-occurrence of multiple psychological conditions has been called the "premier challenge facing mental healthprofessionals". While much discussion has been given to the potential effects this co-occurrence might have on treatments for children and adolescents, very little hard data exist on the topic, especially within mental health service settings. The proposed study is designed to investigate the relation between syndrome co-occurrence and (1) the process of child psychotherapy, (2) therapy engagement, and (3) treatment outcome among 463 children and their parents receiving mental health services at one of ten community clinics in Southern California. This study takes a dimensional approach to co-occurrence, in which main effects of syndromes will be used to quantify the independent impact of each syndrome and statistical interactions among different syndromes will be used to quantify the impact of co-occurrence. Multi-level or hierarchical linear modeling will be used to predict treatment process, therapy engagement, and outcomes over two years post intake from individual syndromes and their interactions. The proposed research will shed light on the debate about effects of syndrome co-occurrence on treatment and enrich our understanding of the factors that contribute to process, engagement, and outcomes within service settings for children.